Azimuth mirror (how to use it)

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On this webpage you'll be referred to the photos listed above

An Azimuth mirror is for taking Celestial bearings (Star bearings) and Terrestrial bearings (Land bearings)

If asked to take a bearing during an Oral Exam, find these things out;

(1) Is it a land or star bearing? (it's a LAND bearing (Terrestrial) even if its a church spire put the Arrows DOWN , if it's a STAR bearing (Celestial) then put the Arrow's UP)

(2) Is the arrows on the thumbscrew up or down?

(3) The Azimuth ring piece, make sure its furthest away from you
(as in photo 6)

In Picture (1) the two round ball shapes are quadrant correctors which contain soft iron this helps take the magnetism away from the compass.

 In Picture (2) you can see the top of the flinders bar, this is your ships head and will be aligned with the lubber line of your compass.

Authors tips when using an Azimuth Mirror

(1) When taking a bearing make sure the ring piece of the Azimuth Mirror is furthest away from you don't have it at your side of the compass.

(2) After lining up the bearing look into the compass bowl to see roughly what bearing you should get.

(3) When moving the thumbscrew, move it slowly, if you get small numbers of degrees then you have reversed the bearing (remember its a mirror) keep it going till you see the correct bearing.

(4) Give the Captain the bearing.

(5) If he asks if you have one of these on your vessel, say yes you have a magnetic compass but most small vessels don't have an Azimuth Mirror

Troubleshooting why you cant get the bearing !!!!

(1) The Captain has his hand over the Compass glass blocking you from taking the bearing (Nasty)

(2) As in number (5) in the photo above The shades are blocking the bearing your trying to take , move them aside

(3) If the Azimuth is on top of a Magnetic compass then its a magnetic bearing and if on top of a gyro compass then its a gyro bearing.

If asked to change the compass bearing to a true bearing, use the saying

(C-D-M-V-T) Cadbury's Dairy Milk Very Tasty, as follows;

Compass Questions

(Q) How do you maintain a magnetic compass?
(a) By keeping it clean and oil the gymbals and making sure there is no air-bubbles in the compass bowl.

(Q) How do you air out of a magnetic compass?
(a) By undoing the thumbscrews that hold the magnetic compass into the gimbals, taking it down to a manageable height and turn it so the screw is topmost, undo the screw and using a syringe fill it up with industrial alcohol or distilled water.

(Q) Why do you need a liquid in a magnetic compass?
(a) To slow the needle down and stop wear and tear on the pivot the needle is sitting on top of.

(Q) Why are you using industrial alcohol or distilled water?
(a) Because they have a high freezing temperature.

(Q) What is variation and deviation?
(a) Combination of Compass Errors

(Q) What is deviation?
(a) The difference between Compass North and Magnetic North.

(Q) What is variation?
(a) The difference between Magnetic North and True North.

(Q) What causes deviation?
(a) The ships magnetic pull. (steel or electric sources can affect the pull on the magnetic compass)

(Q) What causes variation?
(a) The Earths magnetic pull.

(Q) How often do you check your magnetic compass for deviation?
(a) As often as possible if you have a gyro compass on your vessel, if not then when approaching a harbour using the leading lights or at sea using two oil-rigs in transit with each other.

(Q) How do you check your magnetic compass for deviation?
(a) By aligning the leading lights and checking your lubber line to see your bearing your steering, compare the two and this gives you compass error, apply the variation from the chart and this leaves your deviation.

(Q) Show me how you would do this?

(Q) You have two degrees West for deviation, where do you log this into?
(a) The deviation log book.

(Q) What is the purpose of a deviation log book?
(a) To keep an eye on your deviation to make sure it does not deviate from the deviation card.

(Q) You have checked your deviation, is this deviation for every point on the compass?
(a) No, the deviation is only for that one course, the course you took the bearing for.

(Q) Can you check your magnetic compass at sea for deviation?
(a) Yes by aligning up two oil-rigs in transit

(Q) How do you check a gyro compass for error?
(a) By doing the same as the magnetic compass.

(Q) Show me?

(Q) You have found the gyro is 001 degree high is this for every point on the compass?
(a) Yes, a Gyro compass has no deviation or variation

(Q) Can you check a magnetic compass for deviation against a gyro compass?
(a) Yes, if the gyro has no error then the gyro is reading a true bearing.

(Q) What if the gyro had an error can we still check a magnetic compass for deviation against a gyro compass?
(a) Yes as long as you knew what the error was (High or low errors)

(Q) Show me?

(Q) If the gyro error was high what direction would the error be?
(a) If the Gyro compass is higher than True North then the Error is a Westerly Error.

(Q) If the gyro error was low what direction would the error be?
(a) If the Gyro compass is lower than True North then the Error is an Easterly Error.

(Q) Can you check your magnetic compass for deviation lying between two vessels tied to the pier?
(a) No, there is too much metal around you, your compass needle will be drawn towards the other vessels.

(Q) Can you check your magnetic compass for deviation lying next to a pier, there are no vessels near your vessel?
(a) No, there are steel girder's built into the pier.

(Q) Can you check your magnetic compass for deviation lying next to a wooden pier that has no steel in it?
(a) Yes, by using a large scale chart of the harbour, finding out the true bearing of the pier your alongside, and comparing it to your compass bearing.

(Q) Can you only take one bearing at that pier?
(a) No, if you turned your vessel around you could check your deviation for that new bearing.

(Q) How do you do a compass swing?
(a) By using a transit bearing from two points of land and check your compass every 20^o

(Q) Who does Magnetic and Gyro compass adjusting in the UK?
(a) A person who holds a Certificate of Competency of compass adjuster.

(Q) What do you use to taking bearings with?
(a) Compass, visual and radar bearings.

(Q) How do you take a compass bearing?
(a) By using an Azimuth Mirror.

(Q) How could you take a compass bearing if you don't have an Azimuth Mirror onboard your vessel?
(a) By taking a relative bearing using radar.

(Q) Show me?

(Q) How can you find your ships position at sea?
(a) By using G.P.S. (Global Positioning Satellite)

(Q) How can we find our ships position 2 miles from a point of land, you have radar, a magnetic compass and charts?
(a) By taking a compass bearing of the point of land then applying deviation to it to give you a magnetic bearing apply variation to give you a true bearing then reversing the bearing, go onto the chart and find the point of land using a set of parallel rules lay off the true reversed bearing and slide it onto the point of land draw a line towards the sea, you have to be on this line somewhere, measure 2 miles from the side of the chart and from the point of land measure it onto your true reversed bearing, where the two intersect is your ships position.

(Q) Would you be happy with just one point of land?
(a) No, Two or even three points of land would give you a better fix.

(Q) How can you check your ships position alongside an oilrig, you have radar, a magnetic compass and charts?
(a) By taking a compass bearing of the oilrig then applying deviation to it to give you a magnetic bearing apply variation to give you a true bearing then reversing the bearing, go onto the chart and find the oilrig using a set of parallel rules lay off the true reversed bearing and slide it onto the oilrig draw a line away from the oilrig, you have to be on this line somewhere, measure 2 miles from the side of the chart and from the oilrig measure it onto your true reversed bearing, where the two intersect is your ships position.

(Q) What is a true meridian?
(a) From you anywhere in the world looking at the North or South Poles.

(Q) What is a Magnetic Meridian?
(a) From you anywhere in the world looking at the Magnetic North or South Poles.

(Q) What is the container at the fore side of a compass binnacle called?
(a) The Flinders Bar

(Q) What is the Flinders' Bar used for?
(a) To Compensate for the errors caused by the ships magnetic field, to take deviation away from the magnetic compass

(Q) Gyro Compass, why is this affected by local anomalies?
(a) (Caution this is a trick question that came out of the exam room), gyro compasses cannot be affected by variation or deviation, it can only be affected by gyro error